In an era of helicopter parents eager to exploit every competitive edge for their kids, at least two companies have begun selling tests that claim to help match youngsters with the sports they are genetically programmed to play best. The DNA scans, the first of an expected wave of attempts to use genes to enhance athletic performance, can steer children toward games they are most likely to win — and perhaps get scholarships to play, the companies say. The tests also let children — and adults — tailor workouts to their innate skills, the firms say, as well as spot those prone to life-threatening heart problems, concussions and other injuries.